The present invention relates generally means utilizable with fire, smoke, air control or other types of apparatuses which are intended to control the operation of those apparatuses and to, at some preselected time, disengage the drive means from those apparatuses so that they will be free to respond in a preselected manner.
In U.S. Pat. No. 3,580,321, for example, a folding blade fire damper is described wherein a plurality of blades are held in the open position by a cable which is attached to the top of the damper frame and which loops under the damper blade before being attached to a motor energized spool. The damper is moved to the open position by energizing the motor and thereby winding the cable onto the spool to raise the blades against the top of the damper frame. Once the damper is fully opened, the motor will stall and maintain that position either until fusable link melts to release the cable under the blades or until powers cut off the motor thereby allowing spring 66 to act upon the drive shaft of the motor to disengage the motor from the remainder of the gear assembly attached to the spool. In this event, the gravitational or other forces exerted by the blades on the spool causes the spool to unwind and the damper to assume the closed position.
Another type of clutch assembly is illustrated in U.S. Pat. No. 3,665,996 which describes a closure mechanism which allegedly eliminates the necessity of using a fusable link purportedly because the use of fusable links is generally unsatisfactory "due to the delay involved in melting the link which enable the products of combustion to spread." When line voltage is no longer applied to the device described in U.S. Pat. No. 3,665,996, the electromagnet 26 releases armature 27 which enables lever 40 to pivot downwardly carrying with it motor 23 and driving spur gear 43. Spur gears 43 and 44 are thus disengaged, allowing the weight of the curtain carried by wires 3 and 4 through anchor 21 to cause drum 22 to rotate so that the curtain 10 is immediately lowered.
In U.S. Pat. No. 3,739,832, a motor operated overhead grill is described in which the motor, when powering the grill in descent, also loads the spring of an emergency grill opening means, which spring, when called upon to do so, is effective in raising the grill sufficiently to provide an emergency escape or exit opening beneath the grill. In the event of an emergency, a cable which is indirectly attached to a pulley disengages that pulley from the drive motor by disengaging a notch 52 on driving member 50 from driving pin 48 on motor shaft 46 by sliding movement 87 of the driving member 50 along the motor shaft 46. If the driving member 50 is moved into a clearance position from drive pin 48 when the grill is in the fully closed position, the helical spring 36 drives an otherwise free wheeling pulley which in turn causes the grill to move towards a partially open position.
Another such spool arrangement is described in U.S. Pat. No. 3,866,656 wherein a motor operating a geared pulley system is provided for retracting the blades of a folding blade fire damper. Drive means are provided attached to the motor operated system to counteract the frictional forces in the system by driving a portion of it in reverse, thereby allowing the retractive blades to fully extend when the motor is shut off.
In U.S. Pat. No. 1,968,719, an automatically operated fire curtain is described wherein a spring is wound and various parts are locked by the use of a lever 29 and the chain with the fusable link. When a fire occurs, the lever 29 releases the index blade and the spring 22 acts through the gears to move the curtain downward.
Other devices related to this general area are described in U.S. Pat. Nos. 3,156,430; 3,313,338; and 3,665,996.